Increased fluorodeoxyglucose activity of a vascular graft representing a potential pitfall of fluorodeoxyglucose positron emission tomography/computed tomography imaging

Abstract

A 75-year-old man was found to have a right lung nodule on a chest radiograph that was suspicious for a lung malignancy. He was subsequently referred for an 18 F-fluorodeoxyglucose (FDG) positron emission tomography/ computed tomography (PET/CT) scan to evaluate the lung nodule. FDG PET/CT confirmed a solitary 1.1 cm spiculated lung nodule that was FDG-avid (maximum standardized uptake value [SUVmax], 6.3) in the posterior segment of the right upper lobe, suspicious for a primary lung malignancy (A and B, arrows). There was no evidence of nodal or distant disease. Incidentally, there was a distinct increase of FDG activity (SUVmax, 6.1) along the entire course of a left synthetic axillobifemoral bypass graft that was inserted 4 years ago (A and B, arrowheads; urinary bladder, open arrow). No abnormal FDG activity was detected in the native blood vessels. The patient did not have any symptoms or complications related to the vascular graft. The inflammatory markers such as serum C-reactive protein and erythrocyte sedimentation rate, as well as the white blood cell count were not elevated.FDG PET/CT had been reported to be a useful and noninvasive imaging modality for evaluating suspected vascular graft infection. 1 Infection of a vascular graft often results in an increase of FDG activity at the involved site. 1 However, increased FDG activity may also be observed in a noninfected vascular graft although the intensity of uptake was reportedly lower. 2 FDG accumulation in noninfected vascular grafts may be due to chronic inflammation on the surface of the graft. 2 Significant increase of FDG activity in a noninfected vascular graft, as demonstrated in the present case with an SUVmax of 6.1, represents a potential pitfall of FDG PET/CT imaging for the evaluation of vascular graft infection and a risk of false positive results, which may impact subsequent management. Caution should be exercised in such instances particularly when there is an absence of corroborating symptoms and raised inflammatory markers. REFERENCES 1. Keidar Z, Engel A, Hoffman A, Israel O, Nitecki S. Prosthetic vascular graft infection: the role of 18F-FDG PET/CT. J Nucl Med 2007;48:1230-6. 2. Wassélius J, Malmstedt J, Kalin B, Larsson S, Sundin A, Hedin U, et al. High 18F-FDG uptake in synthetic aortic vascular grafts on PET/CT in symptomatic and asymptomatic patients.